Evaluating quantitative and qualitative models: An application for nationwide water erosion assessment in Ethiopia

This paper tests the candidacy of one qualitative response model and two quantitative models for a nationwide water erosion hazard assessment in Ethiopia. After a descriptive comparison of model characteristics the study conducts a statistical comparison to evaluate the explanatory power of the models, using an Ethiopian soil erosion data set as reference. The study, therefore, introduces a generic transformation procedure, whereby qualitative models reproduce quantitative results, while the outcomes of quantitative models are mapped on an ordered (qualitative) classification. The evaluation yields the following results. Application of the USLE model in Ethiopia is restricted by data paucity, while it ranks lowest in the statistical evaluation. However, it provides reliable results in areas where water erosion incidence is low. The Expert model, based on easily available data and expert judgements, covers a wide variability of the explanatory variables, which makes it suitable for a nationwide assessment. It is the second-best model in the statistical evaluation. Yet, its qualitative output complicates the assessment of the dynamic changes in soil productivity characteristics, while the postulated additive form of the logit model is not appropriate to assess erosion hazard. The quantitative AccDat model has the highest predictive power and is based on easily available data, but has a frail empirical basis and its application at a nationwide scale requires a careful interpretation. The varying performances in the different areas of the data domain justify the selection of a combination of models for a nationwide erosion assessment, rather than a single 'best' model.

[1]  Luca Montanarella,et al.  Soil erosion risk assessment in Europe , 2000 .

[2]  G. R. Foster,et al.  A Process-Based Soil Erosion Model for USDA-Water Erosion Prediction Project Technology , 1989 .

[3]  R. J. Rickson,et al.  Modelling regional soil erosion susceptibility using the Universal Soil Loss Equation and GIS. , 1994 .

[4]  C. Rose,et al.  Soil Erosion Models and Implications for Conservation of Sloping Tropical Lands , 2002 .

[5]  Michiel A. Keyzer,et al.  A non-parametric analysis of qualitative and quantitative data erosion modelling: a case study for Ethiopia , 1999 .

[6]  Jay Gao,et al.  A Holistic Approach Towards Assessment of Severity of Land Degradation Along the Great Wall in Northern Shaanxi Province, China , 2003, Environmental monitoring and assessment.

[7]  Michiel A. Keyzer,et al.  Using the mollifier method to characterise data sets and models. The case of the universal soil loss equation , 1997 .

[8]  Mark A. Nearing,et al.  A nonparametric/parametric analysis of the Universal Soil Loss Equation , 2003 .

[9]  Ben Sonneveld,et al.  Formalizing the use of expert judgements for land degradation assessment: a case study for Ethiopia , 2002 .

[10]  Saro Lee,et al.  Soil erosion assessment and its verification using the Universal Soil Loss Equation and Geographic Information System: a case study at Boun, Korea , 2004 .

[11]  W. G. Matlock,et al.  Desertification of Arid Lands , 1977 .

[12]  D. H. Yaalon.  Comments on “A Unifying Quantitative Analysis of Soil Texture” , 1989 .

[13]  Julius Juma Okello,et al.  Adoption and adaptation of natural resource management innovations in smallholder agriculture: reflections on key lessons and best practices , 2009 .

[14]  G. R. Foster,et al.  Predicting soil erosion by water : a guide to conservation planning with the Revised Universal Soil Loss Equation (RUSLE) , 1997 .

[15]  Mark A. Nearing,et al.  Error Assessment in the Universal Soil Loss Equation , 1993 .

[16]  C. G. Weeramantry.  The impact of technology on human rights , 1994 .

[17]  R. J. Rickson,et al.  Conserving soil resources: European perspectives. , 1994 .

[18]  M. Watson,et al.  Main Report , 2006, Genetics in Medicine.

[19]  T. Tin,et al.  Geophysical Research Abstracts , 2007 .

[20]  P. J. Albersen,et al.  Water erosion assessment based on expert knowledge and limited information using an ordered logit model , 1999 .

[21]  James R Frankenberger,et al.  Regional Scale Application of USLE and WEPP for Soil Erosion Assessment in Korea , 2007 .

[22]  Larry Boersma,et al.  A Unifying Quantitative Analysis of Soil Texture1 , 1984 .

[23]  Anita Veihe,et al.  Erosion risk assessment in Ghana using USLE: the role of GIS , 1998 .

[24]  T. Bontkes,et al.  Agricultural Prices and Land Degradation in Koutiala, Mali: a Regional Simulation Model Based on Farmers’ Decision Rules , 2001 .

[25]  W. Greene,et al.  计量经济分析 = Econometric analysis , 2009 .

[26]  M. Hill,et al.  Multi-Criteria Assessment of Tensions in Resource Use at Continental Scale: A Proof of Concept with Australian Rangelands , 2006, Environmental management.

[27]  Hans Hurni,et al.  Soil Erosion in Huai Thung Choa-Northern Thailand Concerns and Constraints , 1982 .

[28]  Luca Montanarella,et al.  Soil erosion risk assessment in Italy , 1999 .

[29]  Gerard Govers,et al.  Data quality and model complexity for regional scale soil erosion prediction , 2002, Int. J. Geogr. Inf. Sci..

[30]  Leo Stroosnijder,et al.  Measurement of erosion: Is it possible? , 2005 .

[31]  Gerard Govers,et al.  GIS-based simulation of erosion and deposition patterns in an agricultural landscape: a comparison of model results with soil map information , 1995 .

[32]  G. Jacks,et al.  Soil Conservation , 1940, Nature.

[33]  Paul L. G. Vlek,et al.  Assessing the potential of changing land use for reducing soil erosion and sediment yield of catchments: a case study in the highlands of northern Ethiopia , 2007 .

[34]  B. Sonneveld,et al.  Land Under Pressure: The Impact of Water Erosion on Food Production in Ethiopia , 2002 .

[35]  A. J. Thomasson.  World map of the status of human-induced soil degradation: L.R. Oldeman, R.T.A. Hakkeling and W.G. Sombroek, Published by the International Soil Reference and Information Centre (ISRIC) and funded by the United Nations Environment Programme (UNEP). 1990. Price US$25.- (unfolded US$20.-) , 1992 .

[36]  Ckk Gachene,et al.  Evaluation and mapping of soil erosion susceptibility: an example from Kenya , 1995 .

[37]  G. Nyberg,et al.  Effect of organic inputs from agroforestry species and urea on crop yield and soil properties at Wondo Genet, Ethiopia , 2006, Nutrient Cycling in Agroecosystems.

[38]  D. Robinson,et al.  Soil Erosion and Conservation , 1988 .

[39]  Ethiopia,et al.  Ethiopia demographic and health survey, 2000 , 2006 .

[40]  John A. Dearing,et al.  Soil erosion on agricultural land. , 1990 .

[41]  W. H. Wischmeier.  Use and misuse of the universal soil loss equation. , 1976 .

[42]  Yong Xue,et al.  A data fusion approach for soil erosion monitoring in the Upper Yangtze River Basin of China based on Universal Soil Loss Equation (USLE) model , 2003 .

[43]  Donald Gabriëls,et al.  Assessment of Erosion. , 1980 .

[44]  A. Vrieling.  Satellite remote sensing for water erosion assessment: A review , 2006 .

[45]  I. D. L. Foster,et al.  Soil erosion studies; some assessments. , 1990 .

[46]  Joerg A. Priess,et al.  Assessment of soil nutrient depletion and its spatial variability on smallholders’ mixed farming systems in Ethiopia using partial versus full nutrient balances , 2005 .

[47]  Paul van Dijk,et al.  Soil maps as data input for soil erosion models: errors related to map scales , 2010 .

[48]  P. I. A. Kinnell,et al.  The IxEA erosivity index: An index with the capacity to give more direct consideration to hydrology in predicting short-term erosion in the USLE modeling environment , 1995 .

[49]  L. M. Risse,et al.  Slope Gradient Effects on Soil Loss for Steep Slopes , 1994 .

[50]  Jan Nyssen,et al.  Human impact on the environment in the Ethiopian and Eritrean highlands—a state of the art , 2004 .

[51]  Jürgen Schmidt,et al.  Soil erosion : application of physically based models , 2000 .

[52]  Lammert Kooistra,et al.  Spatial variation in biodiversity, soil degradation and productivity in agricultural landscapes in the highlands of Tigray, northern Ethiopia , 2009, Food Security.

[53]  Ben Sonneveld,et al.  Formalizing expert judgements in land degradation assessment: a case study for Ethiopia , 2003 .

[54]  G. Erpul,et al.  Use of USLE/GIS Methodology for Predicting Soil Loss in a Semiarid Agricultural Watershed , 2007, Environmental monitoring and assessment.

[55]  James M. Hamlett,et al.  Statewide GIS-based ranking of watersheds for agricultural pollution prevention , 1992 .

[56]  W. H. Wischmeier,et al.  Predicting rainfall erosion losses : a guide to conservation planning , 1978 .